1. Field of the Invention
The present invention relates to a developing method and a developing apparatus each for exposing a resist film formed on a substrate such as a semiconductor wafer, an LCD substrate, or the like in a predetermined pattern and thereafter developing the exposed pattern.
2. Description of the Related Art
In a coating and developing system for a photolithography process in processes of semiconductor device fabrication, for example, resist coating processing for forming a resist film on the front surface of a semiconductor wafer and developing processing for performing exposure processing for the resist-coated semiconductor wafer and thereafter developing the wafer are performed.
In the developing processing, the wafer which has undergone exposure in a predetermined pattern, post-exposure bake processing and cooling processing is carried into a developing unit to be mounted on a spin chuck. A developing solution is supplied from a developing solution supply nozzle and applied (heaped up) so as to have a thickness of 1 mm, for example, on the entire surface of the semiconductor wafer, and thus a developing solution puddle is formed. The wafer stands still for a predetermined period of time with the developing solution puddle being formed, and developing processing progresses by natural convection. Thereafter, the developing solution is blown off by the semiconductor wafer being rotated by the spin chuck, and then a rinse solution is discharged from a rinse solution supply nozzle to wash away the developing solution remaining on the wafer. Subsequently, the spin chuck is rotated at a high speed, whereby the developing solution and the rinse solution remaining on the semiconductor wafer are blown away so that the wafer is dried. Thus, a series of developing processing is completed.
When the developing solution puddle is formed in this developing processing, nozzles of various shapes are used for applying the developing solution onto the entire surface of the semiconductor wafer, and the wafer is rotated and the nozzle is scan-moved while the developing solution is being discharged from the nozzle.
In the aforesaid prior developing method, however, the time to heap up the developing solution, impact at the time of supply of the developing solution, displacement speed of the developing solution, and the like are uneven in the surface of the semiconductor wafer by any means when the developing solution puddle is formed on the semiconductor wafer, thereby making it difficult to obtain uniformity of line width. Moreover, defects are prone to occur due to entrance of bubbles in heaping up the liquid and the like.
Recently, with high integration of devices from 64 megabytes to 256 megabytes, it is increasingly demanded to make circuit patterns more minute, and the minimum line width almost reaches a super-submicron region of not more than 0.2 xcexcm. In order to meet the demand, a chemically amplified resist is used as a resist capable of micromachining, but the chemically amplified resist has poor wettability for the developing solution, so that the aforesaid defects are prone to occur. When micromachining is performed with the chemically amplified resist, the ununiformity of line width due to the aforesaid unevenness becomes remarkable.
An object of the present invention is to provide a developing method and developing apparatus in each of which line width can be made uniform and defects do not tend to occur during the coating of the developing solution.
To attain the above object, a first aspect of the present invention is a developing method for exposing a resist film formed on a substrate in a predetermined pattern and thereafter developing the exposed pattern, comprising the steps of (a) applying a solution having a photosensitive radical onto the entire upper surface of the resist film on the substrate, (b) applying a developing solution onto the entire upper surface of the applied solution, and (c) exposing the entire surface of the solution having the photosensitive radical applied onto the resist film.
A second aspect of the present invention is a developing method for exposing a resist film formed on a substrate in a predetermined pattern and thereafter developing the exposed pattern, comprising the steps of (a) applying a solution having a photosensitive radical onto the entire upper surface of the resist film on the substrate, (b) applying a developing solution onto the entire upper surface of the applied solution, and (c) exposing the entire surface of the solution having the photosensitive radical applied onto the resist film via the developing solution and developing the resist film by the developing solution and the dissolved solution.
A third aspect of the present invention is a developing apparatus for exposing a resist film formed on a substrate in a predetermined pattern and thereafter developing the exposed pattern, comprising a first coating mechanism for applying a solution having a photosensitive radical onto the entire upper surface of the resist film on the substrate, a second coating mechanism for applying a developing solution onto the entire upper surface of the applied solution, and an exposure mechanism for exposing the entire surface of the solution having the photosensitive radical.
It is preferable to form an interlayer between the solution having the photosensitive radical and the resist film. If the solution having the photosensitive radical directly touches the resist film when the solution having the photosensitive radical is an organic series, the resist dissolves in the solution, whereby the interlayer is provided to prevent the above phenomenon. In this case, it is preferable to use water soluble resin, for example, polyvinyl alcohol (PVA) is used as the interlayer. A water soluble solution is preferable as the solution having the photosensitive radical. In this case, the interlayer is not necessarily needed.
Moreover, it is preferable to perform an all-at-once exposure step after a developing solution applying step in terms of certain progress of the developing of the resist film all at once. Even if the developing solution applying step is performed after the all-at-once exposure step, a coating film of the solution having the photosensitive radical dissolves in the developing solution, whereby time difference in the start time of developing of the resist film is not prone to occur. Accordingly, the developing solution applying step may be performed after the all-at-once exposure step.
A G-line resist solution can be used as the solution having the photosensitive radical. The G-line resist has a function of raising the developing rate by being dissolved by the developing solution, which can reduce the developing time nearly to half.
According to the present invention, the solution having the photosensitive radical is applied onto the resist film, and the developing solution is applied thereonto, and thereafter the entire surface of the solution having the photosensitive radical is exposed all at once, for example, whereby developing of the resist film progresses all at once after the coating film of the solution having the photosensitive radical dissolves in the developing solution. Consequently, time difference in the start time of developing does not occur in the surface of the substrate, thereby enabling uniform developing and improving line width uniformity (CD value uniformity) in the surface of the substrate. Further, since developing progresses all at once after the developing solution is applied, the time to heap up the developing solution is not restricted and the reduction of impact of the developing solution and the like do not need to be considered. As a result, a developing solution nozzle can be structured more simply. Furthermore, the developing solution does not directly attack the resist film, thereby decreasing defects.
These objects and still other objects and advantages of the present invention will become apparent upon reading the following specification when taken in conjunction with the accompanying drawings.